Integrated Covalent Organic Framework/Carbon Nanotube Composite as Li‐Ion Positive Electrode with Ultra‐High Rate Performance

Abstract

low specific capacity of 73 mAh g −1 at 500 mA g −1 in a Li-ion cell. However, the electrochemical performance was greatly enhanced by forming the tube-type core-shell structure of the composites (DAPQ-COFX). Using this approach, we achieved specific capacities of up to 162 mAh g −1 at 500 mA g −1 . By varying the composition of the DAPQ-COFX composite, it was found that DAPQ-COF50, which contained 50 wt% of CNT, exhibited the highest utilization of the redox-active sites (95%). Notably, the DAPQ-COF50 composite presents the best rate performance in COF-based electrode materials reported so far, facilitating ultrafast charge/discharge rates as high as 50 A g −1 -this means that the device can be fully charged in just 11 s.

A Pyrene-4,5,9,10-Tetraone-Based Covalent Organic Framework Delivers High Specific Capacity as a Li-Ion Positive Electrode

“…Encouragingly, the C=O bond feature reforms when the electrode is recharged, and the spectrum of the charge electrode appears almost identical to that of the pristine electrode. This observation, consistent with our earlier work on the analogous 2-carbonyl 9,10-phenanthrequinone-based COF, 26 supports that the reversible charge storage involves the redox electrochemistry of the carbonyl (C=O) of the DAPT structure. For the 4-carbonyl containing PT-COFX composite materials, the earlier CVs ( Figure 2 a) indicate two prominent reaction peaks separated by ca.…”

“…As shown in Table S4 , the capacity of PT-COF50 outperforms that of other related COF-based composite cathodes. 12 − 14 , 16 , 17 , 26 , 32 , 33 , 36 , 37 …”

“… 19 For example, we recently reported a phenanthraquinone-containing COF that we used to form carbon nanotube (CNT) composite cathodes for Li-ion batteries, demonstrating 95% utilization of the carbonyl redox-active sites. 26 However, although all the carbonyl groups were electrochemically redox-active and the COF/CNT composite allowed for ultrafast charging times, the overall capacity was limited by the 157 mAh g –1 theoretical specific capacity of the COF. 26 Here, we designed composites containing a pyrene-4,5,9,10-tetraone COF (PT-COF, Figure 1 a) that has a much higher concentration of redox-active carbonyl groups and a theoretical capacity that is ca.…”

“… 26 However, although all the carbonyl groups were electrochemically redox-active and the COF/CNT composite allowed for ultrafast charging times, the overall capacity was limited by the 157 mAh g –1 theoretical specific capacity of the COF. 26 Here, we designed composites containing a pyrene-4,5,9,10-tetraone COF (PT-COF, Figure 1 a) that has a much higher concentration of redox-active carbonyl groups and a theoretical capacity that is ca. 73% higher ( Figure S2 ); the same COF was also investigated recently as a supercapacitor.…”

Eight‐Electron Redox Cyclohexanehexone Anode for High‐Rate High‐Capacity Lithium Storage

“…[15,18,27,39,16] New peaks COLi and LiO centered at 1387 and 1060 cm −1 appeared, respectively, which is mainly attributed to the lithiation of CO and the formation of SEI films. [40][41][42] It is demonstrated that the insertion of Li + into CO results in the formation of COLi bond. [43] In addition, a small peak of sp 2 -hybridized carbon (1500-1400 cm −1 ) appeared in such initial discharging process.…”